The organic electroluminescent device is a self-emitting device, and has been actively studied for their brighter, superior viewability and the ability to display clearer images compared with the liquid crystal device.
In 1987, C. W. Tang and colleagues at Eastman Kodak developed a laminated structure device using materials assigned with different roles, realizing practical applications of an organic electroluminescent device with organic materials. These researchers laminated tris(8-hydroxyquinoline)aluminum (an electron-transporting phosphor; hereinafter, simply Alq3) and a hole-transporting aromatic amine compound, and injected the both charges into the phosphor layer to cause emission in order to obtain a high luminance of 1,000 cd/m2 or more at a voltage of 10 V or less (see, for example, Patent Documents 1 and 2).
To date, various improvements have been made for practical applications of the organic electroluminescent device. In order to realize high efficiency and durability, various roles are further subdivided to provide an electroluminescence device that includes an anode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a cathode successively formed on a substrate (see, for example, Non-Patent Document 1).
Further, there have been attempts to use triplet excitons for further improvements of luminous efficiency, and use of phosphorescent materials have been investigated (see, for example, Non-Patent Document 2).
The light emitting layer can be also fabricated by doping a charge-transporting compound, generally called a host material, with a phosphor or a phosphorescent material. As described in the foregoing lecture preprints, selection of organic materials in an organic electroluminescent device greatly influences various device characteristics, including efficiency and durability.
In an organic electroluminescent device, the charges injected from the both electrodes recombine at the light emitting layer to cause emission. The probability of hole-electron recombination can be improved and high luminous efficiency can be obtained by improving the hole injectability and the electron blocking performance of blocking the injected electrons from the cathode, and by thus confining the excitons generated in the light emitting layer. The role of the hole transport material is therefore important, and there is a need for a hole transport material that has high hole injectability, large hole mobility, high electron blocking performance, and high durability to electrons.
The aromatic amine derivatives described in Patent Documents 1 and 2 are known examples of the hole transport materials used for the organic electroluminescent device. These compounds include a compound known to have an excellent hole mobility of 10−3 cm/Vs or higher. However, the compound is insufficient in terms of electron blocking performance, and some of the electrons pass through the light emitting layer. Accordingly, improvements in luminous efficiency cannot be expected.
Arylamine compounds of the following formulae having a substituted carbazole structure (for example, Compounds A and B) are proposed as improvements over the foregoing compounds (see, for example, Patent Documents 3 and 4).

However, while the devices using these compounds for the hole injection layer or hole transport layer have improved luminous efficiency and the like, the luminous efficiency is still insufficient, and the device cannot be said to have a sufficiently low voltage and sufficient current efficiency. Further improvements of luminous efficiency are therefore needed.